Tri-tert-butanol amine acts as promoter with alkali metal salts in the nucleophilic fluorination of alkylsulfonates. It significantly enhances the reactivity of alkali metal salts with minimum formation of side-products (alkene, ether, and alcohol) com-pared to other catalysts in fluorination reaction. The synergism of tert-alcohol and amine moiety plays a pivotal role in fluorination.
Natural polysaccharides supported tetrabutylammonium fluoride (TBAF) complexes are prepared and found to be highly stable and selective fluoride source for well‐renowned nucleophilic (SN2 type) fluorination reactions for the first time. Bacterial cellulose, plant cellulose, pectin, and starch derived TBAF complexes are synthesized, characterized (using SEM, TEM, and NMR techniques) and studied for their stability and reactivity. Heterogeneous bacterial cellulose‐TBAF complex (NBu4(Bac‐cell‐OH)F) 1 was found to be highly stable and non‐hygroscopic among all complexes, which gave high yields of fluorinated products in multi‐gram scale in shorter reaction time. The primarily developed batch protocol was extended to solid‐solid continuous flow reaction using an in‐house built screw reactor, which furnished products in a few seconds of residence time (tR=20–25 sec) and excellent yields.
Fluoroarene-mediated
trifluoromethylation of carboxylic acids for
the synthesis of trifluoromethyl ketones is disclosed. The fluoroarene
activates the acid group and generates the fluoride source in situ for the trifluoromethylation reaction. The present
protocol is safe and metal-free, operates under mild reaction conditions,
and does not require any external additives to generate trifluoromethyl
anion. The current transformation provides good functional group tolerance
and also delivers 92% and 88% yields of trifluoromethyl ketones in
batch and continuous flow, respectively.
A Brönsted acid catalyzed tandem 1,6‐conjugate sequential cycloaddition reaction using 2‐hydroxy‐p‐quinone methides and β‐functionalized ketones is reported. The method allows xanthenones and chromenes to be accessed in moderate to excellent yield with broad substrate scope, which could be further functionalized to give a versatile set of products.
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